This is because of the way proxies are created for handling caching, transaction related functionality in Spring. This is a very good reference of how Spring handles it – Transactions, Caching and AOP: understanding proxy usage in Spring
In short, a self call bypasses the dynamic proxy and any cross cutting concern like caching, transaction etc which is part of the dynamic proxies logic is also bypassed.
The fix is to use AspectJ compile time or load time weaving.